RELATIONSHIP BETWEEN AMBULATORY AND RESTING BLOOD-PRESSURE RESPONSES TO DIETARY SALT RESTRICTION IN NORMOTENSIVE MEN

Objective To examine the relationship between changes in resting and a mbulatory blood pressures induced by dietary salt restriction in 90 yo ung normotensive men. Methods Subjects were given a standardized low-s alt diet containing 20 mmol sodium chloride per day for 14 days, To th is diet, a daily supplement of 20 tablets of slow sodium (10 mmol NaCl per tablet) or placebo was added in a randomized single-blind cross-o ver fashion for 7 days. The ambulatory blood pressure was measured on the sixth day and the resting blood pressure was measured on the seven th day of each dietary period. Results Although salt intake did not af fect blood pressure levels in the whole group, the response of the blo od pressure was quite variable among individual subjects. Salt-induced changes in resting systolic (r = 0.30, P = 0.006) and mean (r = 0.27, P = 0.014) blood pressures, but not diastolic blood pressure, were co rrelated positively to changes in daytime ambulatory blood pressure, T he changes in resting systolic and mean blood pressures were also corr elated significantly to the nocturnal falls in systolic (r = 0.26, P = 0.015) and mean (r = 0.27, P = 0.012) blood pressure levels and heart rate (r = 0.26, P = 0.015) under the high-salt diet. Diet-induced cha nges in resting mean blood pressure were correlated significantly to t he daytime ambulatory blood pressure (r = 0.30, P < 0.005) and the res ting heart rate (r = 0.24, P < 0.02) under the high-salt diet. Conclus ion Salt-induced changes in resting blood pressure in young normotensi ve men are correlated positively to changes in ambulatory daytime bloo d pressure levels as well as to the daytime ambulatory blood pressure and the nocturnal fall in blood pressure under a high-salt diet. These findings suggest that dietary salt-intake restriction can lower both resting and daytime ambulatory blood pressure levels in some normotens ive individuals who may be predisposed to the development of hypertens ion.